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Re: Digital Sextant
From: Vic Fraenckel
Date: 2002 Apr 2, 08:41 -0500
From: Vic Fraenckel
Date: 2002 Apr 2, 08:41 -0500
Dan Allen wrote: | I wonder what kind of silicon sensors exist that act as artificial horizons, | and what kind measure angles, and how accurately? The digital compasses | recently referred to are accurate to 2 degrees. For a sextant the angle | needs to be measured to a few seconds of arc to be competitive. In discussing the Digital Sextant, one must NOT confuse a digital compass with the method of measuring altitude. A sextant is NOT used to measure azimuth so to quote the accuracy of a digital compass module as an argument against the possibility of building a Digital Sextant clouds the issue. I have personally used digital optical encoders that can measure an angle to 360/4096 degrees = 0.088 degrees = 5.27 minutes. The encoder resolves 360 degrees into 4096 counts. While this does NOT come close to what would be needed to make the Digital Sextant, it is a device I am familiar with. There exists encoders that have even higher resolution. There also exists a integrated circuit device (Analog Devices ADXL202) which can measure it's own relationship to the the earth's gravitational field and who's output is a measure of the angles it makes with the gravitational field in two axes. I have used this device as well.. I have interfaced both devices to a microcontroller with ease and made useful measurements with them. Perhaps a Digital Sextant is not so far fetched after all! Vic ________________________________________________________ Victor Fraenckel - The Windman vfraenc1@nycap.rr.com KC2GUI www.windsway.com Home of the WindReader Electronic Theodolite Read the WIND